[PATCH v4] clarify device reset

[Cornelia Huck <cohuck@redhat.com>]

Properly specify that the method for the driver to request a
device reset is transport specific, and some action the device
has to take.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
---

Stefan, Halil: I did not apply your R-b due to the amount of changes.

v3 -> v4:
  - moved device status 're-initialize to 0' clause that is now duplicated
    to an informal description
  - more clarifications on when reset may be used and device requirements
  - use \field{device status} consistently
RFC v2 -> v3:
  - re-worded the "must not send notifications" clause to avoid guessing
  - added a driver conformance clause on how a driver should find out
    when reset is complete
RFC -> RFC v2:
  - moved reset spec to basic facilities

---
 conformance.tex |  2 ++
 content.tex     | 24 +++++++++++++++++++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/conformance.tex b/conformance.tex
index e78adfdbd283..17c390d249db 100644
--- a/conformance.tex
+++ b/conformance.tex
@@ -64,6 +64,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
 \begin{itemize}
 \item \ref{drivernormative:Basic Facilities of a Virtio Device / Device Status Field}
 \item \ref{drivernormative:Basic Facilities of a Virtio Device / Feature Bits}
+\item \ref{drivernormative:Basic Facilities of a Virtio Device / Device Reset}
 \item \ref{drivernormative:Basic Facilities of a Virtio Device / Device Configuration Space}
 \item \ref{drivernormative:Basic Facilities of a Virtio Device / Virtqueues}
 \item \ref{drivernormative:Basic Facilities of a Virtio Device / Message Framing}
@@ -283,6 +284,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
 \begin{itemize}
 \item \ref{devicenormative:Basic Facilities of a Virtio Device / Device Status Field}
 \item \ref{devicenormative:Basic Facilities of a Virtio Device / Feature Bits}
+\item \ref{devicenormative:Basic Facilities of a Virtio Device / Device Reset}
 \item \ref{devicenormative:Basic Facilities of a Virtio Device / Device Configuration Space}
 \item \ref{devicenormative:Basic Facilities of a Virtio Device / Message Framing}
 \item \ref{devicenormative:Basic Facilities of a Virtio Device / Virtqueues / The Virtqueue Descriptor Table}
diff --git a/content.tex b/content.tex
index 1ca24c13f2d0..47239b877c6c 100644
--- a/content.tex
+++ b/content.tex
@@ -51,6 +51,9 @@ \section{\field{Device Status} Field}\label{sec:Basic Facilities of a Virtio Dev
   an error from which it can't recover.
 \end{description}
 
+The \field{device status} field starts out as 0, and is reinitialized to 0 by
+the device during reset.
+
 \drivernormative{\subsection}{Device Status Field}{Basic Facilities of a Virtio Device / Device Status Field}
 The driver MUST update \field{device status},
 setting bits to indicate the completed steps of the driver
@@ -71,7 +74,6 @@ \section{\field{Device Status} Field}\label{sec:Basic Facilities of a Virtio Dev
 \end{note}
 
 \devicenormative{\subsection}{Device Status Field}{Basic Facilities of a Virtio Device / Device Status Field}
-The device MUST initialize \field{device status} to 0 upon reset.
 
 The device MUST NOT consume buffers or send any used buffer
 notifications to the driver before DRIVER_OK.
@@ -193,6 +195,26 @@ \section{Notifications}\label{sec:Basic Facilities of a Virtio Device
 terminology. Occasionally, the term event is used to refer to
 a notification or a receipt of a notification.
 
+\section{Device Reset}\label{sec:Basic Facilities of a Virtio Device / Device Reset}
+
+The driver may want to initiate a device reset at various times; notably,
+it is required to do so during device initialization and device cleanup.
+
+The mechanism used by the driver to initiate the reset is transport specific.
+
+\devicenormative{\subsection}{Device Reset}{Basic Facilities of a Virtio Device / Device Reset}
+
+A device MUST reinitialize \field{device status} to 0 after receiving a reset.
+
+A device MUST NOT send notifications or interact with the queues after
+indicating completion of the reset by reinitializing \field{device status}
+to 0, until the driver re-initializes the device.
+
+\drivernormative{\subsection}{Device Reset}{Basic Facilities of a Virtio Device / Device Reset}
+
+The driver SHOULD consider a driver-initiated reset complete when it
+reads \field{device status} as 0.
+
 \section{Device Configuration Space}\label{sec:Basic Facilities of a Virtio Device / Device Configuration Space}
 
 Device configuration space is generally used for rarely-changing or
-- 
2.26.2